Glossary of terms

1"25.4 millimetres (mm)
1m335.315 cubic feet (cu.ft)
1m3424 board feet (bf)
1Mbf2.36 cubic metres (m3)
BfBoard feet
BmBoard measure
ChecksLongitudinal separation of the fibres in wood that do not go through the whole cross section. Checks result from tension stresses during the drying process.
DecayThe decomposition of wood substance by fungi (other terms: rot, dote)
DensityWeight per unit volume. Density of wood is influenced by rate of growth, percentage of late wood and in individual pieces, the proportion of the heartwood.
Dimensional StabilityA term that describes whether a section of wood will resist changes in volume with variation in moisture content (other term: movement in performance).
DurabilityThe resistance of wood to attack by decay fungi, insects and marine borers.
FASHighest quality NHLA grade
FigureThe pattern produced in a wood surface by annual growth rings, rays, knots, deviations from regular grain, such as interlocked and wavy, and irregular colouration.
FlitchA log or part of a log, trimmed and prepared for conversion into veneers, or part of a converted log suitable for further conversion.
GrainThe direction, size, arrangement, appearance, or quality of the fibres in sawn wood. Straight grain is used to describe lumber where the fibres and other longitudinal elements run parallel to the axis of the piece.
Gum PocketAn excessive local accumulation of resin or gum in the wood.
HardnessThe resistance of wood against indentation and abrasion. Values are given in Newtons (N) and are a measure of the load required to embed an 11.3mm ball to one half its diameter in the wood.
HardwoodA description applied to woods from deciduous and evergreen broad-leaved trees (Angiosperms). The term has no reference to the actual hardness of the wood.
HeartwoodThe inner layers of wood in growing trees that have ceased to contain living cells. Heartwood is generally darker than sapwood, but the two are not always clearly differentiated.
KilningThe process of drying lumber artificially under scientifically controlled conditions. Kilns are the chambers used for this process.
LumberThe American term for converted wood or sawn timber. Lumber mills and sawmills are terms used to describe the processing units that carry out this conversion.
m2square metres
m3cubic metres
MbfThousand board feet
Modulus of ElasticityAn imaginary stress necessary to stretch a piece of material to twice its length or compress it to half its length. Values for the individual species are given in megapascals (MPa - equivalent to N/mm2), and are based on testing small clear pieces of dry wood. The values given on page 25 are based on testing full sized pieces.
Moisture Content (M.C.)The weight of water contained in wood expressed as a percentage of the weight of the oven dry wood.
PARPlaned (surfaced) all round (same as S4S)
Pith FlecksPith-like irregular discoloured streaks of tissue in wood, due to insect attack on the growing tree.
Quarter/rift sawnLumber that is cut from the log on or near to the radial axis to produce ?edge?, ?straight? or ?vertical? grain patterns.
RWLRandom widths and lengths
S2SSurfaced 2 sides
S4SSurfaced (planed) 4 sides (same as PAR)
SapwoodThe outer zone of wood in a tree, next to the bark. Sapwood is generally lighter in colour than heartwood but lacks resistance to decay.
ShrinkageThe contraction of wood fibres caused by drying below the fibre saturation point (usually around 25-27% M.C.). Valves are expressed as a percentage of the dimension of the wood when green.
SmSurface measure
Specific GravityThe relative weight of a substance compared with that of an equal volume of water. S.G. values given are based on wood volume at 12% M.C. and oven dry weight.
SplitSeparation of the fibres in a piece of wood from face to face (other term: end-split).
StainA variation from the natural colour of the wood or a discoloration that may be caused by micro-organisms, metal or chemicals. The term also applies to materials used to impart colour to the wood.
SurfacedThe American term that is used to describe lumber that has been planed.
TallyThe American term for lumber measure. (Green tally refers to measurement before kilning and net tally to measurement after kilning.)
TextureDetermined by relative size and distribution of the wood elements. Described as coarse (large elements), fine (small elements) or even (uniform size of elements).
WarpDistortion in lumber causing departure from its original plane, usually developed during drying. Warp includes cup, bow, crook and twist.
WeightThe weight of dry wood depends upon the cellular space, ie the proportion of wood substance to air space. Values are given for each species in kg/m3 at 12% M.C.